This invention relates to dentistry and in particular to devices and methods for gingival retraction and localized conditioning as a step in complex dental procedures including tooth reconstruction and treatment.
Gingival retraction and conditioning is a time-consuming and somewhat traumatic procedure. It is required for example, in the process of fabricating tooth crowns which must seat well into the sub-gingival areas around the tooth, not to exceed the depth of the sulcus. To cast the crown, a precision mold must be taken of the tapered prepared tooth to the extremes of the prepared gingival trough, which is the tiny open groove between the gingival tissue and the ground-down neck or prepared portion of the tooth, so that the fabricated crown will extend into the sub-gingival area and also mate perfectly with all opposing tooth surfaces. To make an accurate mold, the gingival trough must be kept open and freed of blood, saliva and debris in a process known as gingival retraction.
An early and largely superseded technique of gingival retraction involves the use of a malleable copper sleeve filled with impression material and adapted to be carefully pressed and manipulated over a tooth to stress and distend the gingiva and squeeze out the blood and saliva from the trough, after which the impression is taken. It is an accurate but painstaking procedure, difficult to do well, often wasteful of time and traumatizing to the gingival tissue.
The state of the art technique for gingival retraction superseding copper sleeves, involves looping an absorbent cord preferably treated with a vasoconstricting chemical such as aluminum chloride about the freshly prepared tooth and packing it into the gingival trough using a pointed instrument. Packing the cord into the trough is tedious and wasteful of time (as much as five minutes) because of poor visibility in an extremely confined area coupled with the inherent sponginess of gingival tissue which resists the cord placement. The cord remains in place for several minutes holding the trough open, absorbing saliva and blood in the trough, and treating the traumatized tissue to control further bleeding. It is withdrawn an instant before the critical impression is taken. In addition to the time taken by the dentist installing the cord and the inherent traumatizing of the tissue, the cord has limited absorption ability and does not effectively protect the general area from the influx of additional saliva.
Further, the stressful action of packing the cord can create an artificially enlarged gingival trough extending beyond the sub-gingival line where tooth preparation ends, even to the point of occasionally tearing gingival tissue from the tooth root beyond the sulcus. The subsequent impression not infrequently yields a crown casting having a skirt which extends beyond the prepared portion of the tooth into an area in which the tooth may widen in an almost imperceptible bulge or bump and thereafter narrow into an undercut. The inherent resilience of the polymerized or hardened impression material enables it to be pulled from the undercut over the enlargement, but the memory of its existence endures. As a result, the finished crown, having a rigid elongated skirt smaller at its leading edge than the widest diameter of the tooth parts it is intended to surround, can bind in a slightly elevated position requiring the dentist to perform tedious grinding operations in an attempt to achieve good crown seating and tooth occulusion. This highly undesirable and time-wasting characteristic has become increasingly evident as less malleable and harder casting metals are substituted for costly softer metals such as gold.
Accordingly, it is an object of the present invention to provide a dental device and method for gingival retraction and conditioning which are able without trauma and in a fraction of the time presently required to carry an absorbent medium into the tiny gingival trough around the necks of prepared teeth to absorb all saliva and blood, to entrain particulate debris, to treat against further bleeding and to shield the entire area from encroaching saliva.
A further object of the invention is to provide a dental device and method for gingival retraction and conditioning which do not enlarge the gingival trough beyond its natural elastic limits and thus beyond the line of tooth preparation and which, therefore, result in impressions which yield castings that do not bind before seating fully on the prepared tooth.